First method:
- Turn on the device.
- Now press the Menu key.
- Then goto Settings -> Privacy -> Factory data reset -> Reset phone -> Erase everything.
- After that your phone will reset and reboots.
Second method:
- Power on the device.
- Next press the emergency call.
- After that tap this code: *#*#2846579#*#* and press Factory Reset.
Third method:
- Power off your phone.
- Next press and hold Volume Up + Power button for about 15 seconds.
- Then you will see Android recovery menu.
- From the menu select "Factory reset/wipe data" using Volume Down to scroll option, and press Power button to accept.
- Now browse option "Yes-detele all user data", and confitm that with Power button.
- After that press Power button to accept option "reboot system now".
